85 305 in a k1500 - wont idle after smog removal

[bbgbouncer]

Thanks for any help here. I looked through past threads and didnt find what I needed.

Situation 85 k1500 with 305. Runs like a champ. stock setup. My 15yr old daughter just bought this. It is covered in oil. We start replacing the valve cover gaskets. I get to looking at all the smog items, vacuum lines, smog pump. I says to myself "we dont need all this garbage". rip it off.

Now it wont idle. it starts fine. I have turned up the idle screw (in effort to solve the issue) now it revs high on start. then drops to what should be idle and dies. you can keep it going a a high idle (sorry no tach) but if you try to let is low idle it tries to die. I have to pump/feather the pedal to keep it going.

I have plugged up all the vacuum ports. hooked the vacuum assist on the distributor to a vacuum port behind the carb in the intake manifold.

It does look like a Qjet. any thoughts?

 

[WP29P4A]

Your probably going to need to be more specific about what you removed and what you BELIEVE is smog garbage that is not needed, to give someone the big picture of what is going on. Did you remove the vapor canister? Did you move the distributor vacuum advance from ported to non ported vacuum, did it go to a temperature switch on it's way to the Dist advance before you removed the vacuum lines? Did you get rid of the ball? Vacuum diaphragm/reservoir.

I can guarantee the next person to comment will ask for pictures too, it helps to see what we are trying to help you fix. @SirRobyn0 should have some helpful info soon also on where to start. Have you downloaded a vacuum diagram for your truck yet?

 

[SirRobyn0]

Your probably going to need to be more specific about what you removed and what you BELIEVE is smog garbage that is not needed, to give someone the big picture of what is going on. Did you remove the vapor canister? Did you move the distributor vacuum advance from ported to non ported vacuum, did it go to a temperature switch on it's way to the Dist advance before you removed the vacuum lines? Did you get rid of the ball? Vacuum diaphragm/reservoir.

I can guarantee the next person to comment will ask for pictures too, it helps to see what we are trying to help you fix. @SirRobyn0 should have some helpful info soon also on where to start. Have you downloaded a vacuum diagram for your truck yet?

Thanks for tagging me Mike, I've got a little more work to do on the farm then I'll give some better thoughts than this, but my knee jerk reaction is that stuff was put there for a reason, and most of the smog stuff by the 80's did more for the engine than just reduce emissions. With that said if done correctly, with some things left intact, it should be able to run fine depending on what was removed.

Yes, pictures would be helpful.

A list of what you removed or disconnected as best you can even if you do not know all the names would help us to guide you.

Check to make sure you didn't leave any vacuum ports open, it almost sounds like a large vacuum leak but could be other things too.

If you removed a lot of the vacuum lines I hope you still have them, because some of the check valves are out of production and you need to keep your ESC system intact, or bypassed or it'll ping once you get the idle worked out.

More later.

 

[SirRobyn0]

Ok I'm going to try to summarize my thoughts a bit feel free to ask questions if you want to.

I'm not trying to harp on this, but when your back on if you could let us know what you removed that would be helpful. Pictures would also be helpful.

The following components that some people think are emissions devices, and must be hooked up. Please note this is not all inclusive it's just what I can think of.

-Tip in sensor - used by ESC system to prevent pinging
-Distributor - vac advance can
-EFE - this takes the place of the heat riser and while it is technically an emissions control device, these engines were built to have them and without you may have cold runability issues when in lower temps.
-Thermac - this is on the air cleaner, again these engines were built to have them and without you may have cold runability issues when in lower temps.
-EGR valve - again an emissions control device, but it controls emissions by lowering the combustion chamber temp, which reduces ping. Without seriously reducing timing, or vac advance a 305 will ping badly without a functional EGR, like engine damaging bad. Unlike the 350, the 305 was built to have an EGR and without other changes it can't be without one.
-vapor canister - if you have removed that you'll need to put some sort of filter on the vent line to the gas tank, but even still it will no longer be a closed system, moisture will get into the tanks and they will rust over time.
-Air pump - if you're running a cat, it will function better, last longer, if the air pump is intact and functional, that included the vacuum lines and switches for it. Those components, will also lengthen the life of the muffler and tail pipe (s).

If your truck is equipped with a 700R4 there is a vacuum switch by the brake master cylinder that some people think is emissions but it's not. Without the vacuum line, vacuum delay, and hooked up properly the torque converter clutch will not operate properly and the transmission will run hotter, have a shorter life and the fuel mileage will go down.

The thing a lot of guys don't realize is the 305 while sharing the same small block as the 350, the 305 was built during the smog era and was built to have those devices, unlike the 350 where the emissions devices were added on.

As to why it won't idle, got to get the additional info from you, and pics from around where you removed stuff would help.

Hopefully this post has been of help, if not at least informative.

 

[85K304SPD]

Doesn't the 85 305 have the electronic q jet? I believe that there is a ecm involved in the timing etc... I dont think the distributor has vac advance. Is there an O2 sensor?
I have an 85 Trans am with this set up, and I still haven't completely figured it out. I hope somebody has more info on how to make it all work.

 

[scrap--metal]

hooked the vacuum assist on the distributor to a vacuum port behind the carb in the intake manifold.

Did you move the distributor vacuum advance from ported to non ported vacuum

I always thought vacuum advance was supposed to run off a ported vacuum source on the carburetor?

If the vacuum advance was reconnected to a non-ported manifold vacuum source, if wouldn't idle the same as it did before removing the smog stuff. Then messing with the idle screws only brought you farther from your initial starting point.

 

[scrap--metal]

Doesn't the 85 305 have the electronic q jet? I believe that there is a ecm involved in the timing etc... I dont think the distributor has vac advance. Is there an O2 sensor?

MOST 305s from '85 will have an electronic quadrajet, but I don't think the electronics are necessary for it to run. I ran mine for years w/o the electronics before eventually changing to an older quadrajet.

An HEI distributor from an '85 does have a vacuum advance canister, but does not have an O2 sensor. The electronics were not that advance yet.

Your Trans Am may be a little different though. Not sure...

EDIT: SirRobyn0 prompted a little more research... The electronic carbs do work in combination with an O2 sensor. I've never paid attention to where this O2 sensor lives (or lived). My K10 had the carb unplugged when I bought it, and it's been that way ever since I owned it.

 

[dvdswan]

Welcome to the site.

 

[85K304SPD]

All that stuff makes a person want to just remove all that stuff and put in a good old 350 with a Edelbrock, Holley and headers. Keep it simple. I guess thats why so many did just that!

 

[SirRobyn0]

Ok guys I'm not gonna take the time to tag ya I assume you'll see this.

Not all 305's had electronic feedback carburetors, some did some didn't. A 305 in a C/K10 is much more likely to have a feedback carb than one in a C/K20.

All 305's in these trucks at least by the early 80's have some kind of spark control. If it's a TBI motor then the main ECM fully controls it. If it's carbed then it has an ESC system which essentially all that system does is listens for knock and retards timing if needed.

The 305 will not react the same to stripping the emissions devices as the 350 does. As I said before the 350 had these emissions devices added on over time. The 305 was built to have them, and unless other changes are made to the engine it will suffer if the emissions devices are simply removed.

 

[scrap--metal]

@SirRobyn0 thanks for the insight. I was unaware that K10 and K20 305's would be equipped with different carburetors from the factory. Doesn't seem to make sense from a production standpoint, but I believe it.

You're comments also got me thinking about that electronic feedback on the carbs. Apparently the system works with an O2 sensor that I never knew about. I always thought the electronic feedback carbs were an integral part of the ESC system, but it's actually a separate system. I updated my previous post accordingly. Sorry @85K304SPD for the misinformation. Thankfully there are enough good minds on this site to keep us all in line.

I disagree with @SirRobyn0 regarding the 305 being built to have these systems in place though. I think that's too general of a statement. Electronic spark control and electronic feedback carburetors did not exist in the mid-70's when the 305 was introduced. Even if those technologies were in development, they certainly were not in production. Those systems can be removed from a 305, just like a 350, if the ignition and carb are tuned for it. Other systems may be more necessary.

 

[Bextreme04]

@SirRobyn0 thanks for the insight. I was unaware that K10 and K20 305's would be equipped with different carburetors from the factory. Doesn't seem to make sense from a production standpoint, but I believe it.

You're comments also got me thinking about that electronic feedback on the carbs. Apparently the system works with an O2 sensor that I never knew about. I always thought the electronic feedback carbs were an integral part of the ESC system, but it's actually a separate system. I updated my previous post accordingly. Sorry @85K304SPD for the misinformation. Thankfully there are enough good minds on this site to keep us all in line.

I disagree with @SirRobyn0 regarding the 305 being built to have these systems in place though. I think that's too general of a statement. Electronic spark control and electronic feedback carburetors did not exist in the mid-70's when the 305 was introduced. Even if those technologies were in development, they certainly were not in production. Those systems can be removed from a 305, just like a 350, if the ignition and carb are tuned for it. Other systems may be more necessary.

While they didn't exist at the time the 305 was introduced, the 80's 305 is not the same engine. The biggest issue is that the head design and the mechanical setup of the engine components in the 80's engines made them very susceptible to detonation. crap compression, huge quench area, small valves.... its a cluster

 

[SirRobyn0]

@SirRobyn0 thanks for the insight. I was unaware that K10 and K20 305's would be equipped with different carburetors from the factory. Doesn't seem to make sense from a production standpoint, but I believe it.

You're comments also got me thinking about that electronic feedback on the carbs. Apparently the system works with an O2 sensor that I never knew about. I always thought the electronic feedback carbs were an integral part of the ESC system, but it's actually a separate system. I updated my previous post accordingly. Sorry @85K304SPD for the misinformation. Thankfully there are enough good minds on this site to keep us all in line.

I disagree with @SirRobyn0 regarding the 305 being built to have these systems in place though. I think that's too general of a statement. Electronic spark control and electronic feedback carburetors did not exist in the mid-70's when the 305 was introduced. Even if those technologies were in development, they certainly were not in production. Those systems can be removed from a 305, just like a 350, if the ignition and carb are tuned for it. Other systems may be more necessary.

I want to respond to certain things you said so I will quote you and after that.
" I was unaware that K10 and K20 305's would be equipped with different carburetors from the factory. Doesn't seem to make sense from a production standpoint, but I believe it."
My understanding is it has to do with emission requirements, and weight ratings. So a C10 would likely have a feedback carb, but because a C20 has a higher GVWR it's under different emission requirements and gets a normal carb. Unless it's sold in California then it gets the feedback carb. Also as time went on emission standards got tougher so more feedback carbs. It's really hard for me to say accurately that one truck or another did or did not get a feedback carb, but the simplified version is it was all about meeting emission requirements.

"regarding the 305 being built to have these systems in place though. I think that's too general of a statement. Electronic spark control and electronic feedback carburetors did not exist in the mid-70's when the 305 was introduced. Even if those technologies were in development, they certainly were not in production. Those systems can be removed from a 305, just like a 350, if the ignition and carb are tuned for it. Other systems may be more necessary."
Perhaps I was a bit to general, but that's why I added the bit about 80's. @Bextreme04 explains it exactly as I understand it. The 80's 305 is not the same as the 70s 305, mainly due to head changes, and the ESC system was implemented at the same time. The 80's 305 cannot be without the systems I mentioned in my other post without other modifications (detuning basically) to keep it from pinging.

 

[Bextreme04]

The emissions equipment being different for C/K10 and C/K20 is absolutely correct. It is also different within C/K20 based on GVWR. My 80 K20 did not come with cats or EGR because it is an 8600GVWR option, which pushed it into "heavy duty emissions" compared to a standard C/K20 that was below that rating and therefore fell into light duty emissions. California emissions are also different and have their own break points and differences.

 

[scrap--metal]

..."heavy duty emissions" compared to... light duty emissions.

Very interesting. I didn't know there was that much variability in these trucks for the same engine size in the same production year, but now I do!

The 80's 305 is not the same as the 70s 305, mainly due to head changes

Nor was I aware of the differences among 305s... Makes me wish I still had the 305 from my Monte Carlo. I don't remember seeing dished pistons in that engine when it was apart, but my '85 305 definitely has low compression dished pistons in it.

That satisfies my learning for the day. Hopefully the OP will learn something in this thread too!